Differential pressure gauge

ABSTRACT

This invention relates to a differential pressure gauge in which the base has an inlet passage connectable to a source of fluid pressure and an outlet passage left open to the atmosphere. A transparent bowl is removably attached to the base by means of a lock ring. The sensing element of the gauge is connected to the inlet so as to respond to the fluid pressure therein while, at the same time, responding to the ambient conditions inside the bowl. The resulting differential pressure reading is transferred to a dial by an indicator responsive to the action of the sensing element.

United States Patent Vander Horst DIFFERENTIAL PRESSURE GAUGE JohnVander Horst, Lakewood, Colo.

Wilkerson Corporation, Englewood, Colo.

Filed: June 21, 1971 Appl. No.: 155,110

Inventor:

Assignee:

References Cited UNITED STATES PATENTS 11/1966 Miller 73/431 1/1922Middleton r 1. 73/407 R 6/1968 Whiting v 1. 73/407 R 4/1970 Bohenek73/431 Oct. 2, 1973 FOREIGN PATENTS OR APPLICATIONS 491,881 9/1938 GreatBritain 73/412 [57] ABSTRACT This invention relates to a differentialpressure gauge in which the base has an inlet passage connectable to asource of fluid pressure and an outlet passage left open to theatmosphere. A transparent bowl is removably attached to the base bymeans of a lock ring. The sensing element of the gauge is connected tothe inlet so as to respond to the fluid pressure therein while, at thesame time, responding to the ambient conditions inside the bowl. Theresulting differential pressure reading is transferred to a dial by anindicator respon sive to the action of the sensing element.

5 Claims, 2 Drawing Figures PATENTED 2|975 3.762.224

INVENTOR JOHN VAN R HORST TO N S DIFFERENTIAL PRESSURE GAUGE In theaverage plant pneumatic system, it is important to know the differentialfluid pressure as this is the working pressure available to operate thevarious machines, tools and other equipment serviced thereby.Differential pressure gauges, for the most part, are expensive andoftentimes difficult to install. Some differential gauges are ill-suitedfor use in pneumatic systems because of the ease with which they becomecontaminated and either stop working altogether or else give falsereadings.

Probably one of the most bothersome problems with the prior artdifferential pressure gauges is the difficulty of disassembling them toclean the dial and glass or plastic cover therefor should these elementsget dirty as they often do. Fogging due to condensate formation mayrender a gauge useless from a practical standpoint if it cannot be read;yet, to take it off the line and disassemble it to remove the condensedmoisture is both a time-consuming and difficult task which is seldomperformed.

n the other hand, uncovered gauge dials provide no solution to theproblem in the average industrial plant because they are too easilydamaged. A bent needle may be hard to detect at a distance and the falsereading it indicates can be more of a problem than no reading at all.

It has now been found in accordance with the teaching of the instantinvention that these and other shortcomings of the prior artdifferential pressure gauges can, in large measure, be eliminated and ata fraction of the cost by means of the simple, yet unobvious expedientof removing the cover glass from an ordinary gauge and then connectingthe sensing element thereof to the high pressure available within theinlet of a conventional pneumatic system drain body before covering thedial with a transparent bowl held inplace by a quick-disconnect ring.The normal outlet passage in the drain body is left open to theatmosphere and the differential pressure across the sensing element isindicated directly on the face of the dial by the needle that sweepsthereacross.

The dial remains clearly visible through the transparent bowl, yet, isadequately protected by the latter. If, perchance, the dial or bowl orboth become dirty or fogged, it takes but an instant to remove the clampring and lift the bowl free of the body so that the dial face can bewiped clean. A quick pass at the inside of the bowl removes any film ofdirt, oil or moisture therefrom preparatory to locking it back in place.This complete disassembly, cleaning and reassembly operation can beperformed in a few minutes time without shutting down the pneumaticsystem or even removing the gauge therefrom.

It is, therefore, the principal object of the present invention toprovide a novel and improved differential pressure gauge.

A second object is the provision of a unit of the type aforementionedthat is ideally suited for use in a pneumatic system.

Another object of the invention forming the subject matter hereof is toprovide a pressure gauge that can be cleaned and serviced withoutdisconnecting it from the line or shutting the latter down.

Still another objective is the provision of a differential pressuregauge that can be disassembled, cleaned and reassembled in a fewminutes.

An additional object is to provide a pressure gauge that can beintegrated quite easily, simply and inexpensively into most allindustrial air systems.

Further objects are to provide a differential pressure gauge that isversatile, rugged, accurate, safe, reliable and even decorative inappearance.

Other objects will be in part apparent and in part pointed outspecifically hereinafter in connection with the description of thedrawings that follows, and in which:

FIG. I is a diametrical section through the pressure gauge of thepresent invention, portions of the dial having been broken away toexpose the sensing element", and,

FIG. 2 is a top plan view of the body alone.

Referring next to the drawings for a detailed description of the presentinvention and, initially, to FIG. 1 for this purpose, reference numeral10 has been selected to designate the differential pressure gauge in itsentirety while number 12 similarly denominates the body atop which isremovably attached a bowl or bubble 14 by means of a quick-disconnectlock ring 16. Mounted inside the bowl in position to be viewedtherethrough is the pressure responsive mechanism which has been broadlyreferred to by numeral 18 and which includes a sensing element 20contained within a housing 22 covered by a dial 24 that is swept by anindicator needle 26.

In FIGS. 1 and 2, the body 12 will be seen to comprise a casting havinga fluid passage 28 that includes a right angle bend and opens upwardlyinto the center of the bowl. This curved passage is connected to receiveair from the service line in which the differential pressure is to bemeasured. As will become apparent presently, no fluid passes through thebody so it must be connected in a blind branch of the service line inorder to not interrupt the flow therethrough. A simple T-connectionwill, of course, suffice for this purpose.

In the particular form shown, the body has an integrally formedupstanding central boss 30 from which passage 28 emerges and this bossis partially encircled by a trough 32 that is intersected by a secondpassage 34. The latter passage opens onto the exterior of the body andis left open to the atmosphere thus placing the interior of the bowl atambient pressure.

In the embodiment illustrated, the body is provided with an upwardlyfacing circular ledge 36 out over which project a plurality ofcircumferentially spaced tongues 38. A complementary set of tongues 40project inwardly from the lower margin of the lock ring 16 in positionto pass downwardly therebetween and lock therebeneath upon limitedrelative rotational measurement.

A second upturned ledge 42 of lesser diameter than ledge 36 encirclesthe body at a higher level thereon and provides a resting place for themarginal flanges 44 bordering the bowl l4. Flange 44 is external andengages beneath the inturned annular flange 46 on the top of the lockring 16. Thus, when the bayonet joint defined by the interlockingtongues carried by the body and lock ring is complete, the bowl issecurely, though detachably, connected to the body.

In the particular form shown, the cylindrical wall surface 48 of thebody 12 that lies directly above ledge 42 is provided with an annularO-ring groove 50 into which O-ring 52 is placed. This O-ring engages theinside wall of the bowl as shown and forms a fluid tight seal therewith.When the body is used as a part of the differential pressure gaugeforming the subject matter hereof, the bowl will contain no fluid norwill it be pressurized; therefore, seal 52 is surplusage except for thefact that it keeps the bowl from rattling under the nearly constantvibration of the air system.

The lock ring 16 has already been described in some detail and it willsuffice to point out additionally that it will ordinarily include somekind of spring latch (not shown) of conventional design that drops intoplace between the tongues when the latter are engaged as shown thuspreventing relative rotational movement between the ring and body.Integral ribs 54 on the outside of the ring provide fingerholds thatassist the operator in turning same relative to the body.

The bowl or bubble 14 is usually molded from clear transparent plasticso as to form a window through which the dial 24 can be viewed and readwith minimal distortion. it should, perhaps, be mentioned that the bowlshown is designed to be viewed as illustrated or inverted so that thegauge dial will be seen through the cylindrically curved wall. in theevent the unit was to be mounted so that the gauge dial would be seenfrom the top of the bubble, it might be preferable to redesign the bowlto' provide a top wall 56 of uniform thickness to look through, all ofwhich is well within the skill of an ordinary designer.

Again with reference to FIG. 1, the pressureresponsive mechanism will beseen to include a nipple 58 that screws into the fluid passage 28 andforms a continuation thereof that projects axially up into the bowl fromthe top of boss 30 where it passes into housing 22 and connects onto thesensing element 20. The housing in the particular form shown comprises ashallow cup-shaped element with the dial 24 covering the open endthereof. The sensing element 20 comprises a bourdon tube in theparticular form illustrated although it may well comprise any of theseveral wellknown mechanisms that will react quantitatively to a pair ofpressures impressed thereacross such as, for example, bellow typesensors and the like. it is important in this connection that thehousing 22 that encases the sensing element be left open to theatmosphere inside the bowl and that the latter, in turn, be incommunication with ambient conditions outside the unit. Accordingly, thecasing 22 is not sealed nor does the dial cooperate therewith to definea sealed chamber as is often the situation with this type of unit whenthe bourdon tube is isolated from the atmosphere and placed in aconstant-pressure environment and calibrated to read absolute pressures.

The free end of the bourdon tube sensing element is linked to the usualgear segment 60 which is mounted on pivot 62 and meshes with gear 64connected to the indicator needle 26. The needle is mounted atop aspindle 66 that piercesthe center of the dial in the customary manner.so that the needle will sweep the face thereof.

Now, in the event the inside of the bowl becomes dirty or fogged bycondensed moisture therein, a simple twist of the lock ring will freethe bowl from the body where it can be wiped clean in an instant. Thesame procedure is followed to clean the face of the dial. The bowl, onthe other hand, adequately shields the dial face, needle and sensingelement from damage What is claimed is:

1. The differential pressure gaugewhich comprises:

a body having an air passage therein with an inlet and an outlet;pressure responsive sensing means in a housing and connected to receiveair from the air passage when the inlet of the latter is connected to apressurized source thereof and move in relation to the pressuredifferential to which it is thus subjected; open faced dial means insaid housing including scale indicia located adjacent the sensing means;indicator means connected to the sensing means and operative uponactuation of the latter to move relative to the dial means and indicatethe differential pressure thereon; and, means comprising a transparentdome detachably connected by locking means to the body, the body and thelocking means interlocked so as to define a vented chamber housing theopen-faced dial means and associated indicator while providing aprotective cover therefor.

2. The differential pressure gauge as set forth in claim 1 in which: thesensing means comprises a bourdon tube.

3. The differential pressure gauge as set forth in claim 1 in which: thedome comprises a molded plastic bowl with a cylindrical wall surfacedefining the window through which the dial is viewed.

4. The differential pressure gauge as set forth in claim 1 in which: thedome and body are detachably interconnected by a quick-disconnectbayonet-type coupling.

5. The differential pressure gauge which comprises:

a body having an air passage therein with a first air passage thereinwith an external inlet and an internal outlet and a second air passagewith an internal inlet and an external outlet;

a pressure responsive sensing means in a housing and connected to theinternal outlet of said first air passage to receive air from the firstair passage when the latter is connected to a pressurized source thereofand move in relation to the pressure differential to which it is thussubjected;

means comprising a transparent dome detachably connected to the body toform a chamber for the housing of the sensing means, said domecommunicating with the second air passage;

an open-faced dial means in said housing and communicating the interiorof the chamber and including scale indicia located adjacent the sensingmeans; and,

indicator means connected to the sensing means operative upon actuationof the latter to move said indicator means relative to the dial andindicate the differential pressure between the first air passage and theinterior of the chamber whereby the openfaced dial and associatedindicator are contained within and protected by the transparent dome.

1. The differential pressure gauge which comprises: a body having an airpassage therein with an inlet and an outlet; pressure responsive sensingmeans in a housing and connected to receive air from the air passagewhen the inlet of the latter is connected to a pressurized sourcethereof and move in relation to the pressure differential to which it isthus subjected; open faced dial means in said housing including scaleindicia located adjacent the sensing means; indicator means connected tothe sensing means and operative upon actuation of the latter to moverelative to the dial means and indicate the differential pressurethereon; and, means comprising a transparent dome detachably connectedby locking means to the body, the body and the locking means interlockedso as to deFine a vented chamber housing the open-faced dial means andassociated indicator while providing a protective cover therefor.
 2. Thedifferential pressure gauge as set forth in claim 1 in which: thesensing means comprises a bourdon tube.
 3. The differential pressuregauge as set forth in claim 1 in which: the dome comprises a moldedplastic bowl with a cylindrical wall surface defining the window throughwhich the dial is viewed.
 4. The differential pressure gauge as setforth in claim 1 in which: the dome and body are detachablyinterconnected by a quick-disconnect bayonet-type coupling.
 5. Thedifferential pressure gauge which comprises: a body having an airpassage therein with a first air passage therein with an external inletand an internal outlet and a second air passage with an internal inletand an external outlet; a pressure responsive sensing means in a housingand connected to the internal outlet of said first air passage toreceive air from the first air passage when the latter is connected to apressurized source thereof and move in relation to the pressuredifferential to which it is thus subjected; means comprising atransparent dome detachably connected to the body to form a chamber forthe housing of the sensing means, said dome communicating with thesecond air passage; an open-faced dial means in said housing andcommunicating the interior of the chamber and including scale indicialocated adjacent the sensing means; and, indicator means connected tothe sensing means operative upon actuation of the latter to move saidindicator means relative to the dial and indicate the differentialpressure between the first air passage and the interior of the chamberwhereby the open-faced dial and associated indicator are containedwithin and protected by the transparent dome.